Moisture cure non-isocyanate acrylic coatings

ABSTRACT

An acrylic polymer having pendant alkoxysilane comprising the free radical reaction product of a polysiloxane, an N-alkylphosphonate N-oxylalkyl ester initiator; and ethylenically unsaturated monomers. The acrylic polymer can be further crosslinked with reactive polysiloxanes.

This application is a divisional application, claiming the benefit of,commonly owned application Ser. No. 10/327,323, filed Dec. 20, 2002 nowU.S. Pat. No. 7,074,856.

BACKGROUND

Many high performance, high solids coating compositions in the art arebased on polymeric systems comprised of either polyester-based orpolyacrylic-based polyols and crosslinking agents thereof. Thesecoatings are generally supplied as two component or “two-pack” systems.In a typical two-pack system, the crosslinking agent is combined shortlybefore application, with curing being conducted at ambient or elevatedtemperatures. While two pack systems often provide high performanceproperties like corrosion and humidity resistance, resistance tosolvents, ultraviolet stability and gloss retention there are notablelimitations. Two-pack systems utilizing isocyanate crosslinkers requirespecial handling and storage operations to prevent premature reactionwith moisture and to avoid human exposure. Further, the components oftwo-pack systems can only be mixed shortly prior to use and once mixedmust be used and ultimately be discarded. Another disadvantage ofisocyanate-crosslinking systems is that the quality of the coating iscompromised by bubble formation during thick film application. A moredesirable coating composition is an ambient curing, one component orone-pack system where all of the coating ingredients are combined into asingle, storage stable mixture. At the same time the one-pack systemshould exhibit the same high performance film properties as a two-packsystem and be isocyanate free.

The coating composition of the present invention is a one-pack acrylicsystem that has the desired film properties of two-pack polyurethanecoatings, such as corrosion and humidity resistance, short dry times,chemical resistance, good ultraviolet resistance and high glosspotential. The coating is moisture-curable, isocyanate-free, and VOCcompliant, with a high solids content (>70% by weight) and a low VOC (<3pounds per gallon). On exposure to moisture, the applied coatingcomposition of the invention is a crosslinked reaction product ofbis-silylamine and an acrylic polymer having pendant alkoxysilanegroups. The acrylic polymer may also have pendant epoxy groups.

The prior art teaches moisture curable coatings formed from(meth)acrylate polymers containing pendant alkoxysilyl groups. These aredescribed in U.S. Pat. Nos. 3,453,136; 3,453,230; 4,603,064; 4,614,777;5,017,668; and 5,705,651. U.S. Pat. No. 5,399,607 discloses a mixture ofacrylic resins with hydroxyl and alkoxysilyl containing acryliccopolymers to make moisture curable coatings.

U.S. Pat. No. 4,789,710 depicts silanated resins reacted withamino-silanes and further reacted with an isocyanate-functionalalkoxysilane. U.S. Pat. No. 5,017,668 describes a long chainamino-silane monomer copolymerized to make a curable acrylic silanepolymer. U.S. Pat. No. 5,459,205 discloses a process to make moreflexible coatings based on moisture curable resins having long pendantsilane-containing moieties. These resins are prepared from silanecontaining macromonomers copolymerized with conventional monomers. Themacromonomers may contain aminosilane moieties; however, the coatingsrequire baking at 60 EC with a tin catalyst.

U.S. Patent Application 2002/0040102 describes an ambient temperaturecuring coating composition comprising a polysiloxane, analkoxysilyl-functional acrylic polymer, and a curing catalyst. Theinvention further relates to the preparation of analkoxysilyl-functional acrylic polymer.

We have found that coatings consisting of the silane-functional acrylicpolymers and amines, as described in the above prior art, lack thedesired solvent resistance of two-pack urethane coatings. Primaryaminosilanes such as aminopropyltrimethoxysilane, when reacted withsilane-functional acrylic polymers, offer some improved solventresistance. However, according to this invention, it has been found thatcoatings consisting of the same silane-functional acrylic polymers, whenreacted with secondary aminosilanes such as bis-silylamines, exhibitmuch improved solvent resistance rivaling that of two-pack urethanes.

SUMMARY OF THE INVENTION

An ambient temperature curing coating composition comprising thecrosslinked reaction product of:

-   (a) an aminosilane-functional compound, wherein the    aminosilane-functional compound is a bis-silylamine of general    formula:    (R²)_(b)(R¹Y)_(a)Si-Q¹-NH-Q²-(NH-Q³)_(n)-Si(YR¹)_(a)(R²)_(b)    -   n≧0    -   a=3-b    -   b=0, 1, 2    -   each Y is independently a heteroatom, selected from O, N; if Y        is N, then the valency of Y is 2; if Y is O, then the valency of        Y is 1;    -   each R¹ is independently a monovalent radical (e.g., hydrogen,        hydrocarbon including but not limited to alkyl (linear or        brached), cycloalkyl, aryl, allyl, or aralkyl. Preferably, R¹ is        an alkyl of 1-10 carbon atoms. Each R¹ may be the same or        different;    -   R² is a monovalent radical, and can include heteroatoms (e.g.,        oxygen, nitrogen, sulfur) not directly bonded to the silicon        atom, including but not limited to, alkyl (linear or branched),        cycloalkyl, aryl, allyl, or aralkyl. Each R² may be the same or        different.    -   Q¹, Q², Q³ is a divalent bridging group, including but not        limited to an alkylene, but preferably is a C₁-C₁₂ alkylene, and        can be branched or cyclic;    -   each Q can be the same or different; and-   (b) an acrylic polymer having pendant alkoxysilane and optionally    epoxy groups.

This invention also relates to the ambient curing coating compositionabove further crosslinked with a polysiloxane.

This invention also relates to articles having the above-claimed curedcoating compositions on at least one surface thereof.

DETAILED DESCRIPTION OF THE INVENTION

The one-pack moisture-curable coating composition of this inventioncomprises a crosslinked reaction product of a bis-silylamine and anacrylic polymer having pendant alkoxysilane and optionally, epoxygroups.

The bis-silylamine of this invention generally has the formula:(R²)_(b)(R¹Y)_(a)Si-Q¹-NH-Q²-(NH-Q³)_(n)-Si(YR¹)_(a)(R²)_(b)  FORMULA I

-   -   n≧0    -   a=3-b    -   b=0, 1, 2    -   each Y is independently a heteroatom, selected from O, N; if Y        is N, then the valency of Y is 2; if Y is O, then the valency of        Y is 1;    -   each R¹ is independently a monovalent radical (e.g., hydrogen,        hydrocarbon including but not limited to alkyl (linear or        brached), cycloalkyl, aryl, allyl, or aralkyl. Preferably, R¹ is        an alkyl of 1-10 carbon atoms. Each R¹ may be the same or        different;    -   R² is a monovalent radical, and can include heteroatoms (e.g.,        oxygen, nitrogen, sulfur) not directly bonded to the silicon        atom, including but not limited to, alkyl (linear or branched),        cycloalkyl, aryl, allyl, or aralkyl. Each R² may be the same or        different.    -   Q¹, Q², Q³ is a divalent bridging group, including but not        limited to an alkylene, but preferably is a C₁-C₁₂ alkylene, and        can be branched or cyclic;    -   each Q can be the same or different.

For the purpose of the present invention a bis-silylamine is generallyof Formula I described above. Specific examples of these bis-silylaminesare bis-(3-trimethoxysilylpropyl)amine,bis-(3-triethoxysilylpropyl)amine, bis-(3-trimethoxysilyl2-methylpropyl)amine, and bis-(3-triisopropoxysilylpropyl)amine. Alsoincluded are asymmetrical secondary silylamines such asN-(3-triethoxysilylpropyl)-N-(5-triethoxysilylpentyl)amine. Abis-silylamine, namely bis-(3-trimethoxysilylpropyl)amine, under thetradename SILQUEST® A-1170, is available from Crompton Corporation. Thisand similar bis-silylamines can be made according to the methods knownin the art, e.g., as taught in U.S. Pat. No. 4,526,996 (see column 5line 54 through column 11 line 26) and U.S. Pat. No. 5,101,055.

Other examples of bis-silylamines can include bis-silylamines modifiedwith long chain alcohols, branched alcohols, cyclic alcohols, aralkylalcohols such as benzyl alcohols. Generally, the alcohol exchange can beaccomplished by the reaction of bis-silylamine with an alcohol atelevated temperature in the presence of a suitable catalyst. Forexample, SILQUEST® A-1170 may accommodate the exchange of up to sixmoles of alcohol, preferably from one to four moles, most preferably 2.5moles of alcohol. In a preferred process for producing a modifiedbis-silylamine, the bis-silylamine, the appropriate alcohol and suitablecatalyst are charged to the reactor under nitrogen purge and heated to80° C. The reaction can be followed by alcohol distillation and/orinfrared spectroscopy. The preferred catalyst is sodium methoxide from0.01% to 0.1% by weight on the total charge.

The amount of bis-silylamine or modified bis-silylamine present in thebinder composition can be about 1% by weight to about 35% by weightbased on the total weight of binder solids. Binder solids include thebis-silylamine crosslinker, the acrylic polymer having pendantalkoxysilane groups, and any reactive diluent.

The bis-silylamines or modified bis-silylamines are blended with anacrylic polymer having pendant alkoxysilane groups, and optionally epoxygroups. These acrylic polymers with pendant alkoxysilane crosslinkinggroups are related to U.S. Pat. No. 3,453,230, U.S. Pat. No. 5,705,351,U.S. Pat. No. 3,453,136, U.S. Pat. No. 4,026,826, and U.S. Pat. No.4,093,673. Generally, an acrylic polymer having pendant alkoxysilanegroups can be prepared by copolymerising at least two differentethylenically unsaturated monomers whereby at least one of the monomersis an alkoxysilyl-functional ethylenically unsaturated monomer. Examplesof ethylenically unsaturated monomers are acrylic esters such asbutyl(meth)acrylate, methyl(meth)acrylate, ethyl(meth)acrylate,propyl(meth)acrylate, n-hexyl(meth)acrylate, isopropyl(meth)acrylate,isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,cyclohexyl(meth)acrylate, 2,2,5-trimethylcyclohexyl(meth)acrylate,isobornyl(meth)acrylate, lauryl(meth)acrylate, methacrylonitrile, andvinyl compounds such as styrene, acrylonitrile, alpha methyl styrene,vinyl toluene, and vinyl acetate, wherein the notation (meth)acrylatemeans acrylate or methacrylate.

An alkoxysilyl-functional ethylenically unsaturated monomer, in general,can be any one of the above-mentioned ethylenically unsaturated monomersfunctionalized with one or more alkoxysilyl groups. Examples ofethylenically unsaturated monomers functionalized with one or morealkoxysilyl groups are 3-((meth)acryloyloxy)propyltrimethoxysilane whichdenotes either 3-(methacryloyloxy)propyltrimethoxysilane or3-(acryloyloxy)propyltrimethoxysilane,3-((meth)acryloyloxy)propyltriethoxysilane,3-((meth)acryloyloxy)propyltripropoxysilane,[3-((meth)acryloyloxy)propyl]methyldimethoxysilane,[3-((meth)acryloyloxy)propyl]methyldiethoxysilane,[3-((meth)acryloyloxy)propyl]methyldipropoxysilane,[4-((meth)acryloyloxy)butyl]phenyldimethoxysilane,[3-(meth)acryloyloxy)propyl]phenyldiethoxysilane,[3-((meth)acryloyloxy)propyl]phenyldipropoxysilane,[3-((meth)acryloyloxy)propyl]dimethylmethoxysilane,[3-((meth)acryloyloxy)propyl]dimethylethoxysilane,[3-((meth)acryloyloxy)propyl]phenylmethylmethoxysilane and[3-((meth)acryloyloxy)propyl]phenylmethylethoxysilane.3-(Methacryloyloxy)propyltrimethoxysilane, commonly known asγ-methacryloxypropyltrimethoxysilane or 3-(trimethoxysilyl)propylmethacrylate (Silquest A174 from Crompton Corp.) is one of the preferredmonomers in the preparation of the alkoxysilyl-functional acrylicpolymer. Modifications to the alkoxysilyl-functional ethylenicallyunsaturated monomer, such as, for example, replacing the propyl group inSilquest® A174 with longer hydrocarbon chains, branched chains, urethanelinkages, polyesters, etc., can also be made. Optionally, a small amountof vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane,etc. may be added with the Silquest A174. The amount ofalkoxysilyl-functional ethylenically unsaturated monomers present in thepolymer composition can be about 1% to about 50% by weight, preferably10% to 25% by weight, and most preferably, 10% to 15% by weight, oftotal monomer.

The acrylic polymer having pendant alkoxysilane groups can be preparedby addition polymerization of ethylenically unsaturated monomers insolution. The polymerization is preferably carried out in anon-functional volatile solvent, such as xylene, toluene, and otheraromatics, t-butyl acetate, n-butyl acetate, and other ester solvents.In general, suitable solvents include those that will not polymerizewith the monomers, and will not react with the bis-silylamine curingagent or alkoxysilyl functionality. Non-hazardous air pollutants(non-HAPs), non-volatile organic compunds (VOC), halogenated aromaticsolvents such as Oxsol 100 (Occidental Chemical) can also be used asnon-functional volatile solvents.

The acrylic polymer having pendant alkxoysilane groups can also be madein a blend of solvents and/or reactive diluents of suitable lowviscosity. Some or all of the monomers can be pre-dissolved in adiluent, which can be solvents, reactive diluents, or a mixture thereof,but preferably the monomers, together with free radical initiator(s) andany chain transfer agent used, are gradually added to the diluent.Preference is given to the use of a reactive diluent having at least onefunctional group which is substantially non-reactive with theethylenically unsaturated monomers and which is capable of reacting witha curing agent to form a polymer network. In accordance with thisinvention, the reactive diluent is an organic compound of viscosity lessthan 2 Pa·s (20 Poise) at 25° C. The reactive diluent can be apolysiloxane, in which case, the polysiloxane preferably also haspendant alkoxysilyl groups, such as described by the following formula:

wherein each R³ and R⁴ is selected from the group consisting of alkyl,aryl, and alkoxy groups having up to six carbon atoms, reactiveglycidoxy groups, and OSi(OR⁵)₃ groups, wherein each R⁵ independentlyhas the same meaning as R³, each R⁴ is selected from the groupconsisting of hydrogen and alkyl and aryl groups having up to six carbonatoms. Suitable polysiloxanes that can be used in the compositionaccording to the present invention include alkoxysilyl-functionalpolysiloxanes such as DC 3037 and DC 3074 (both from Dow Corning), or SY231, SY 550, and MSE 100 (all from Wacker). Diluents other thanpolysiloxanes can include monomeric alkoxysilanes, such astetraethylorthosilicate, trimethoxypropyl silane and dimethoxydiphenylsilane; and organofunctional monomeric alkoxysilanes, such asglycidoxypropyl trimethoxysilane, and glycidoxypropyl triethoxysilane.

Preferably, the diluent is charged to the reactor, the monomers andchain transfer agent are mixed together as one feed, and the initiatoris added in a separate feed. For example, the diluent can be heated to atemperature in the range of 50-200° C., and the monomers, initiator, andchain transfer agent are added over a period of up to 12 hours,preferably in 3 hours, while the temperature of the solution ismaintained during the addition and for a further period of 0.5 to 4hours after the addition. A further charge of initiator may be addedduring this further period to reduce the level of unreacted monomer.However, it is also possible to reduce this level by distilling off theunreacted monomer from the reaction mixture.

Free radical polymerization is often used in the coatings industry toproduce a wide variety of polymers. Resins with narrow molecular weightdistributions (polydispersity) are desirable because of the decrease inviscosity due to fewer high molecular weight chains. Conventional freeradical solution polymerization produces resins with polydispersities of2 or greater because radical termination by chain coupling leads tohigher molecular weight chains which broadens the molecular weightdistribution and increases the viscosity of the polymer solution.Generally, any of the free radical initiators known to the art can beutilized. Suitable free radical initiators include any of the alkylperoxides such as tert-amyl and tert-butyl peroxides, di-tert-butylperoxide, peresters such as tert-butyl perbenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate,2,5-bis(2-ethylhaxanoyl-peroxy)-2,5-dimethylhexane, or tertiary butylperoctoate, and any of the various known azo initiators such as2,2′-azobisisobutyronitrile. Particularly preferred are2,2′-azobisisobutyronitrile or 2,2′-azo-bis(2-methylbutyronitrile) (Vazo67 from DuPont). For example, the weight of the free radical initiatorused (by weight based on monomers) is generally at least 0.5%. A chaintransfer agent such as (3-mercaptopropyl)trimethoxysilane, A-189(Crompton) is preferably utilized during the free radical polymerizationof the invention. In addition, other chain transfer agents could be usedwith A-189 such as alkyl thiols (e.g. dodecanthiol) and the like. Theamount of chain transfer agent used (by weight based on monomers) isgenerally at least 0.5%, preferably 1 to 10%, or a level of 0.5 to 7%initiator can be used in conjunction with 1 to 10% chain transfer agent.

Controlled radical polymerization reduces polydispersity by reducingtermination reactions. Nitroxyl radicals, for example, can be used incontrolled radical polymerizations to mediate the polymerization andinterfere with the termination reactions by reversibly reacting with apropagating radical. These “living” chains grow at the same rate andproduce polymer chains that are homogenous in length and composition.Preferably, the composition of the monomer feed should be the same inevery chain and every chain should have nearly the same molecularweight. These living chains also allow the formation of block copolymersor tapered block copolymers by sequentially feeding monomers or mixturesof monomers. Generally, nitroxyl radical generating initiators caninclude compounds such as N-alkylphosphonate-N-oxylalkyl esters. MONAMS,which is N-alkylphosphonate-N-oxylmethylpropionate, from Atofina is anitroxide compound that decomposes thermally to produce high solidsresins with narrow polydispersities (Proceedings of the Twenty-NinthInternational Waterborne, High Solids & Powder Coatings Symposium, 6-8Feb. 2002, New Orleans, La., USA pages 197-210). In accordance with thisinvention, the MONAMS nitroxide can be used as a free radical initiatorto synthesize acrylic polymers having pendant alkoxysilane groups.MONAMS can also be used to polymerize monomers in Dow Corning 3074reactive polysiloxane to make polymers having pendant alkoxysilane. Thepolymers can then be formulated with bis-silylamines to produce thecoating composition of this invention.

Preferably, the acrylic polymer having pendant alkoxysilane groupscomprises a mixture of 1% to 50% by weight trimethoxysilylpropylmethacrylate, 1% to 65% by weight methylmethacrylate, 1% to 50% byweight 2-ethylhexyl acrylate, and 1% to 30% by weight styrene in adiluent. The acrylic polymer having pendant alkoxysilane groups can alsobe optionally functionalized with one or more pendant epoxy groups,wherein glycidyl methacrylate is a preferred monomer from 0% to 15% byweight of total monomer charge.

In a preferred embodiment, the coating composition comprises from 1% to35% by weight of the bis-silylamine and from 25% to 99% by weight of theacrylic polymer having pendant alkoxysilane groups, and the remainderbeing other typical coating components known in the art. Optionally, thecoating composition may comprise up to 75% by weight of a polysiloxane.The polysiloxane can be added at several points in the process: 1) asthe diluent for the polymerization, 2) after polymerization or 3) duringthe paint making process.

A coating composition produced from the mixture of thealkoxysilyl-functional acrylic polymer and bis-silylamine is cured byambient moisture, and thus, a secondary curing agent is not necessary toinitiate the curing reaction. To promote rapid cure upon exposure tomoisture, the one component coating composition according to the presentinvention may also comprise a curing catalyst as a secondary component.However, if a curing catalyst is utilized in the coating composition toaccelerate cure, the catalyst is normally packaged separately from thesilane-containing coating composition. The components are mixed togethershortly before application of the coating. The curing catalyst ingeneral can be any curing catalyst active in crosslinking thealkoxysilyl-functional groups present in the acrylic polymer and/orbis-silyl amine and/or in the reactive diluent under the intendedconditions of curing. Examples of general classes of catalysts that canbe used include basic catalysts (amines or inorganic bases), acidiccatalysts (organic and inorganic acids), metal catalysts such astitanium, aluminum, calcium, tin, zirconium, cobalt, etc., and mixturesthereof. The coating compositions of the invention generally cure atambient temperatures, for example 0 to 30° C. The coating compositionsof the invention alternatively can be cured at elevated temperatures,for example from 30° C. to 130° C., to speed up the curing. The VOC forthe coatings described in this invention is below 3.0 pounds/gallon orless than 359 grams/liter. However, near 100% solid coatings having avery low measured volatile organic content can be achieved by the use ofpolysiloxane as a diluent.

Depending on the field of application, the coating compositions of theinvention may further comprise one or more additional ingredients commonto the paint industry. They may comprise one or more pigments, liketitanium dioxide, coloring agents such as yellow or red iron oxide or aphthalocyanine pigment, pigment dispersing agents, light stabilizers,thixotropic agents, and/or one or more strengthening pigments such asmicaceous iron oxide or crystalline silica and/or one or moreanticorrosive pigments such as metallic zinc, zinc phosphate,wollastonite and/or a filler pigment such as barytes, talc or calciumcarbonate. The composition may comprise a thickening agent such asfine-particle sized silica, bentonite clay, hydrogenated castor oil, ora polyamide wax.

The coating compositions of the invention in general can be used asfinish coatings and/or primer coatings. Finished coating compositionsexhibit high gloss which is retained remarkably well on weathering andUV exposure. They are particularly suitable for coating substrates whichare exposed to weather for long periods. The highest levels of gloss maybe achieved if the coating composition includes an organic solvent suchas xylene. The coating composition may also contain an alcohol, e.g.methanol, ethanol or other alcohols which has the added benefit ofimproving stability.

A finish coating according to the invention can be applied over variousunprimed or primed coating surfaces. The coating composition can be usedas a finished coat on concrete, buildings, steel structures,automobiles, aircraft and other vehicles, general industrial machineryand wood. The finished coat can be either pigmented or clear(non-pigmented). The coating composition can also be applied directly tometal substrates like Bonderite, cold rolled steel, galvanized steel,hot dipped steel, blasted steel, and aluminum.

The coating composition of the invention alternatively can be used as aprotective primer coating, particularly on steel surfaces, for examplebridges, pipelines, industrial plants or buildings, oil and gasinstallations, or ships. For this use it is generally pigmented withanticorrosive pigments. Primer coating compositions according to theinvention can be used as maintenance and repair coatings on less thanperfect surfaces such as aged blasted steel, hand-prepared weatheredsteel, and aged coatings. These primer coating compositions can bereadily topcoated, particularly with the coatings of this invention withgood inter-coat adhesion.

The invention will be elucidated with reference to the followingexamples. These are intended to illustrate the invention but are not tobe construed as limiting in any manner the scope thereof.

EXAMPLES Resin Examples 1 & 2 Silanated Polyacrylate Resin Synthesis isShown in Table 1

TABLE 1 Resin Example Component 1 2 Charge Xylene 38.6 25.98 MonomersIsobutylmethacrylate 43.1 Methyl Methacrylate 21.28 2-ethyl hexylacrylate 7.1 20.71 Styrene 13.39 Gamma- 7.8 10.49 methacryloxypropyl-trimethoxysilane Mercaptopropyl- 2.79 trimethoxysilane Initiator Vazo 670.53 1.34 Chase Vazo 67 .05 .25 Xylene 2.9 3.76 NVM* 58% 69%*Non-volatile materialCharge xylene to the reactor and heat to 90° C. Feed monomers andinitiator over 3 hours in a nitrogen atmosphere. Hold for one hour. Heatto 95° C. and feed chase over 3 hours. Heat to 99° C. and hold for onehour. Cool and filter resin through a 150 micron bag.

Crosslinker Examples 3 and 4 Synthesis of bis-silylamine Crosslinker byAlcohol Exchange

TABLE 2 Crosslinker Example Component 3 4 Bis(silyl)amine A-1170 Bis(3-100 51.2 trimethoxysilylpropyl) Amine Alcohol 2-ethylhexanol 48.7Catalyst Sodium Methoxide 0.1Charge the 2-ethyl hexanol, A-1170, and sodium methoxide to the reactor.Heat to 80° C. Turn on nitrogen sparge and collect methanol in a DeanStark trap. Once methanol no longer distills, reaction is complete.Confirm by IR.

Paint Examples 5-8

Paint Examples 5 and 6 are clear paints produced using Resin Samples 1and 2, and Crosslinker Examples 3 and 4. Paint Examples 7 and 8 arecomparative examples that contain primary mono-silylamine crosslinker,3-aminopropyltrimethoxysilane, A-1100 from Crompton Corporation.

TABLE 3 Paint example 5 6 7 8 Resin example 1 1 1 1 Crosslinker example3 4 A-1100 A-1100 Parts by weight: Resin 100 100 100 100 Crosslinker10.70 21.40 6.95 13.85The chemical resistance results of paint examples 5, 6, 7, and 8 arecoated on Bonderite B-1000 panels and cured at 140° F. for 30 minutes.The chemical resistance is tested on the coatings for 24 hours atambient conditions. The results are tabulated in Table 4.

TABLE 4 Paint example 5 6 7 8 Toluene No effect No effect delaminationdelamination Methyl ethyl No effect No effect delamination delaminationketone 10% H₂SO₄ No effect No effect No effect discoloration 10% NaOH Noeffect No effect No effect discoloration

Paint Examples 9-12

Paint Examples 9 and 10 are pigmented paints produced with Resin Example2 and Crosslinker Examples 3 and 4 as described above. Paint examples 11and 12 are comparative examples containing a primary mono-silylaminecrosslinkers such as 3-aminopropyltrimethoxysilane (A-1100), and3-aminopropyltriethoxysilane (A-1110), respectively, both from CromptonCorporation.

TABLE 5 Paint example 9 10 11 12 Resin example 2 2 2 2 Crosslinkerexample 3 4 A-1100 A-1110 Parts by weight: Resin 54.16 52.37 52.99 55.31Crosslinker 5.36 8.49 3.40 2.87 Dispersant¹ 1.72 1.66 1.68 1.76 TiO₂ ²34.42 33.28 33.68 35.15 Xylene 4.33 4.19 8.24 4.91 NVM* 78.00 79.0075.00 77.00 *Non-volatile material by weight ¹Dispersant A-1230 fromCrompton Corporation. ²Titanium dioxide CR-828 from Kerr McGee.The chemical resistance results of paint examples 9, 10, 11 and 12 arecoated on Bonderite B-1000 panels and cured for 30 days at 25° C. and50% relative humidity. The chemical resistance is tested on the coatingsfor 24 hours at ambient conditions. The results are tabulated in Table6.

TABLE 6 Paint example 9 10 11 12 Formula 409 No effect No effect Noeffect Visible stain cleaner Ethanol No effect No effect No effectVisible stain Methyl ethyl Visible stain No effect Visible stain Visiblestain ketone Methyl amyl No effect No effect Visible stain Visible stainketone Methyl isobutyl Very slight No effect Very slight Visible stainketone stain stain Unleaded Very slight No effect Very slight Visiblestain gasoline stain stain

1. An acrylic polymer having pendant alkoxysilane groups comprising thefree radical reaction product of: a polysiloxane; and anN-alkylphosphonate N-oxylalkyl ester initiator; and ethylenicallyunsaturated monomers.
 2. A process for preparing an acrylic polymerhaving pendant alkoxysilane groups, comprising: forming nitroxyl ormulti-nitroxyl radicals with an N-alkylphosphonate N-oxylalkyl esterinitiator; combining the nitroxyl or multi-nitroxyl radicals withethylenically unsaturated monomers and a polysiloxane to form an acrylicpolymer having pendant alkoxysilane groups.